On Mon, 22 Sep 2003 14:04:48 GMT, someone who calls themselves Randy
wrote:

Hello,

I have been running a small shop for several years and would now like
to get my first CNC machine. To do this I will need to upgrade my
phase convertor or get 3 phase from the power co.

Unless you want to go with a rotary converter, it's a lot easier in
the long run to let the Power Company provide the 3-phase to you
directly, and unless the other power users sharing that transformer
with you are real power-pigs it's usually cleaner power.

And it's consistent, there's no phase converter to break or wear
out, and no need to play around with balancing capacitors or pony
motors to get a rotary converter started.

The only time I suggest using a phase converter is when the utility
refuses to supply 3Ph (usually to a residence), a hobby shop where it
is only going to be used very occasionally, or if the utility starts
quoting 5-figure prices to extend the third leg line to your
location...

The power co has agreed to hook me to an exsisting 120/240 open delta
supply ,there are two transfromers on the pole and the third leg is
wild, not sure of the exact voltage.

The wild leg is somewhere around 208V to ground. This is why it
gets color-coded orange, and you have to be very careful to never
connect any 120v breakers to that leg. And put BIG warning labels on
the panel that it's a high-leg - I've seen 'handymen' accidentally
plug the breaker for a string of condo-garage fluorescents onto the
House Panel high-leg, and the results aren't pretty. ;-P

I'm going to be extending an existing 240V open-Delta well service
on Wednesday and Thursday to run a grape stemmer-crusher about 700'
away, which is why we're running #4 CU power leg wires for a (for now)
7 amp 3Ph motor load. Voltage drop is a serious concern, and I want
to have a big enough line there for when they need the next size
larger crusher in a few years.

They expect that with the heat in the Malibu hills they'll need to
start picking & crushing grapes by Friday or Saturday. Nothing like
leaving little things like the power line till the last minute... ;-)

(The other choices were a 700' run to a 480V Delta service, or a
1,500' run to a 240V 1PH service and a converter, both not good. The
ranch hands can break a phase converter too easily by plugging the
crusher motor with it jammed, and barbecue themselves "extra-crispy"
by messing around with a hot 480V line.)

-- Bruce --
--
Bruce L. Bergman, POB 394, Woodland Hills CA 91365, USA
Electrician, Westend Electric (#726700) Agoura, CA

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